Search found 13 matches

by Whalertime
Mon Sep 30, 2019 10:08 pm
Forum: REPAIRS and MODIFICATIONS
Topic: 1986 Johnson 70-HP: 18 Questions
Replies: 45
Views: 10099

Re: 1986 Johnson 70-HP: Six Questions

L78: What is the boat speed [of your SPORT 15] with the Johnson 70 at WOT?
by Whalertime
Sun Sep 29, 2019 11:19 pm
Forum: REPAIRS and MODIFICATIONS
Topic: 1986 Johnson 70-HP: 18 Questions
Replies: 45
Views: 10099

Re: 1986 Johnson 70-HP: 18 Questions

Your follow up to this lengthy discussion is good to have. I think you have rescued that classic OMC three-cylinder engine from a undeserved oblivion. Yes I think we did, your responses have been very valuable. Had a nice tube session with my son and daughter on Sat. My daughter did not want to go ...
by Whalertime
Sun Sep 29, 2019 10:54 pm
Forum: REPAIRS and MODIFICATIONS
Topic: 1986 Johnson 70-HP: 18 Questions
Replies: 45
Views: 10099

Re: 1986 Johnson 70-HP: 18 Questions

How far out did you have it trimmed to get 36mph? If not trimmed to the max, that is about what you will get. Did you ask the owner what it used to run when he had it? I was not using the trim at all. When I went 36 mph it was just after I bought the boat (5 years ago) the engine just had a lot mor...
by Whalertime
Fri Sep 27, 2019 12:13 am
Forum: REPAIRS and MODIFICATIONS
Topic: 1986 Johnson 70-HP: 18 Questions
Replies: 45
Views: 10099

Re: 1986 Johnson 70-HP: 18 Questions

I wanted to thank everyone for their thoughts and time on the subject of my Johnson 70. Last week I brought the motor in and we removed and replaced the head gasket. Because of the rust particulate on the spark plug we went through the process of pulling the head. The bolts needed heat and a good de...
by Whalertime
Sun Aug 25, 2019 11:30 am
Forum: REPAIRS and MODIFICATIONS
Topic: 1986 Johnson 70-HP: 18 Questions
Replies: 45
Views: 10099

Re: 1986 Johnson 70-HP: Six Questions

Well I had a little time to investigate yesterday. Sorry I said I had not replaced the fuel lines. What I meant was not recently not since the loss of power concern. About two years ago I replaced all fuel lines including the little tiny lines before the carburetors. I also put a new fuel tank assoc...
by Whalertime
Thu Aug 22, 2019 12:50 pm
Forum: REPAIRS and MODIFICATIONS
Topic: 1986 Johnson 70-HP: 18 Questions
Replies: 45
Views: 10099

Re: 1986 Johnson 70-HP: Six Questions

Sounds like you need a new mechanic. Steam is bad....very bad. What are your compression numbers? That boat properly setup should run 45+. The 3cyl OMCs are the strongest 70hp I have ever driven but I have blown one up. Struggling to plane and low idle says she is probably running on 2cyls. Does yo...
by Whalertime
Thu Aug 22, 2019 12:46 pm
Forum: REPAIRS and MODIFICATIONS
Topic: 1986 Johnson 70-HP: 18 Questions
Replies: 45
Views: 10099

Re: 1986 Johnson 70-HP: Six Questions

I advise you to have the engine serviced by an experienced mechanic who has many years of hands-on work with this 30-year-old engine. Check the boat fuel system for obstructions. Try running the engine on a different fuel tank, fuel hose, and primer bulb assembly. Do not run the engine if the cooli...
by Whalertime
Thu Aug 22, 2019 12:42 pm
Forum: REPAIRS and MODIFICATIONS
Topic: 1986 Johnson 70-HP: 18 Questions
Replies: 45
Views: 10099

Re: 1986 Johnson 70-HP: Six Questions

jimh wrote:A5: the presence of steam in the overboard indicator stream or confidence stream at idle speeds should be interpreted as lack of proper cooling water flow.


I’ll run some salt away through it, and it is possible that I picked something up.
by Whalertime
Thu Aug 22, 2019 12:41 pm
Forum: REPAIRS and MODIFICATIONS
Topic: 1986 Johnson 70-HP: 18 Questions
Replies: 45
Views: 10099

Re: 1986 Johnson 70-HP: Six Questions

A4: the classic OMC three-cylinder 70-HP is perhaps one of the best outboard engines ever made and with proper maintenance could run forever. I completely agree and this is my dilemma. I believe it’s the best motor for the boat which is why I’ve been dumping money into it, I’m just not seeing any r...
by Whalertime
Thu Aug 22, 2019 12:29 pm
Forum: REPAIRS and MODIFICATIONS
Topic: 1986 Johnson 70-HP: 18 Questions
Replies: 45
Views: 10099

Re: 1986 Johnson 70-HP: Six Questions

A3: the maximum horsepower is listed on the capacity plate on the hull. The maximum power is not specified by two-stoke or four-stroke power-cycle engine designs. A further consideration is engine weight. At the time the 15-foot hull was designed, most engines were two-stroke-power-cycle designs an...
by Whalertime
Thu Aug 22, 2019 12:21 pm
Forum: REPAIRS and MODIFICATIONS
Topic: 1986 Johnson 70-HP: 18 Questions
Replies: 45
Views: 10099

Re: 1986 Johnson 70-HP: Six Questions

jimh wrote:A2: if you think air is being pulled into the fuel supply to the engine, temporarily insert a section of clear hose. Observe the fuel flow for bubbles.


That’s a great idea thanks.
by Whalertime
Thu Aug 22, 2019 12:21 pm
Forum: REPAIRS and MODIFICATIONS
Topic: 1986 Johnson 70-HP: 18 Questions
Replies: 45
Views: 10099

Re: 1986 Johnson 70-HP

jimh wrote:A1: A gradual loss of engine speed at full throttle is usually indicative of a problem in fuel delivery.

Thanks I will check the fuel pump, I replaced it once but perhaps it’s time again. I really appreciate everyone’s input. Thanks.
by Whalertime
Wed Aug 21, 2019 11:32 pm
Forum: REPAIRS and MODIFICATIONS
Topic: 1986 Johnson 70-HP: 18 Questions
Replies: 45
Views: 10099

1986 Johnson 70-HP: 18 Questions

I have a 1986 Johnson 70 on my 1986 15-footer. The 1986 Johnson 70 was great for my first four years of ownership. For the last year or more I have been battling constant stalling and a loss of power. I have seen 36-MPH. WOT before. Now maximum boat speed is at 23-MPH WOT and very slow acceleration ...